Wire break detection in redundant communications

ABSTRACT

A system and method for low-cost, fault tolerant, EMI robust data communications, particularly for an EV environment.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/643,794, filed 7 May 2012, the contents of which are expresslyincorporated by reference thereto in its entirety for all purposes.

The following applications are related to the present application, eachalso an application claiming benefit of U.S. Provisional Application No.61/643,794, filed 7 May 2012 and filed on even date herewith, thecontents of these applications are expressly incorporated by referencethereto in their entireties for all purposes: Attorney Docket 20109-7082(application Ser. No. ______) titled ROBUST COMMUNICATIONS INELECTRICALLY NOISY ENVIRONMENTS, Attorney Docket 20109-7083 (applicationSer. No. ______) titled HOST COMMUNICATIONS ARCHITECTURE, AttorneyDocket 20109-7084 (application Ser. No. ______) titled REDUNDANTMULTISTATE SIGNALING, and Attorney Docket 20109-7086 (application Ser.No. ______) titled HOST INITIATED STATE CONTROL OF REMOTE CLIENT INCOMMUNICATIONS SYSTEM.

BACKGROUND OF THE INVENTION

The present invention relates generally to data communications, and morespecifically, but not exclusively, to low-cost, fault tolerant, EMIrobust data communications for high performance electric vehicle (EV)environments.

Increasingly in vehicular and industrial applications, high energyelectrical energy storage systems are used. Whether deployed to energizetraction/propulsion motors, or factory machines, these energy storagesystems often include many interconnected battery module assemblies,each module assembly including many individual battery storage cells.The interconnected modules collectively represent a unitary battery packfor the energy storage needs of the application.

Each module includes on-board electronics for safety and monitoringuses, and it is important that a centralized monitoring system reliablyexchange data with these modules. The voltages and currents that existin operation and control of the motors or machines produce conditions(e.g., voltage and current variations) that can interfere with thecommunications in a number of ways. The communication system musttherefore be designed to operate satisfactorily in the presence ofsignificant potential electromagnetic interference (both electromagneticinduction and electromagnetic radiation).

In the EV context, further boundary conditions include: a) low-costsolutions, b) reduced part/component solutions, c) low powerconsumption, and d) reliability appropriate for an automotiveenvironment. The communications to and from the energy storage systemincludes safety-critical data and the automotive environment is harsh.The vehicle moves and is subject to mechanical bumps, shocks, andvibrations, under a range of temperature and humidity conditions. Themodules are discrete elements and communications systems require wiringharnesses using wires and connectors. The wires and wireconnectors/connections can break and/or they can become loose or provideintermittent connections, among other challenges.

What is needed is a system and method for low-cost, fault tolerant, EMIrobust data communications, particularly for an EV environment.

BRIEF SUMMARY OF THE INVENTION

Disclosed is a system and method for low-cost, fault tolerant, EMIrobust data communications.

The following summary of the invention is provided to facilitate anunderstanding of some of technical features related to low-cost, faulttolerant, EMI robust data communications in an electric vehicle (EV),and is not intended to be a full description of the present invention. Afull appreciation of the various aspects of the invention can be gainedby taking the entire specification, claims, drawings, and abstract as awhole. The present invention is applicable to other environments besideselectric vehicles.

A data communications system, including a plurality of communicationdevices having a first device initiating transmission of data to asecond device; a first single data conductor communicating the data fromthe first device to the second device; and a second single dataconductor communicating the data from the first device to the seconddevice; and wherein the first single data conductor and the secondsingle data conductor are electrically coupled at the second deviceforming a break detection loop; wherein the first device includes a datatransmitter connected to the first single data conductor; and wherein abreak detector is coupled to both the single data conductors and assertsa break signal when detecting a break in one of the data conductors.

A redundant power system, including a host having a power supplyproviding a voltage to a first location and a noise-isolating impedancecoupling the first location to a second location; a single conductorloop having a first end coupled to the first location, a second endcoupled to the second location; a client coupled to the single conductorloop between the locations and preferentially receiving an operatingcurrent from the first location over the single conductor loop when anelectrical communication from the first location to the client isintact, the client secondarily receiving the operating current throughthe impedance when the electrical communication from the first locationto the client is impaired; and a break detector coupled to the singleconductor loop asserting a break signal when the electricalcommunication from the first location to the client is impaired.

A data communications method, including a) initiating transmission ofdata from a first device to a second device; b) communicatingredundantly the data from the first device to the second device using apair of single data conductors electrically coupled at the second deviceforming a break detection loop, the first device including a datatransmitter connected to the first single data conductor; and c)asserting a break signal when detecting a break in one of the dataconductors by use of a break detector coupled to both the dataconductors.

A redundant power provisioning method, including a) providing a voltageto a first location on a host having a power supply with anoise-isolating impedance coupling the first location to a secondlocation on the host; b) coupling the first location to the secondlocation using an external single conductor loop extending from thefirst location to the second location; c) receiving preferentially, at aclient coupled to the single conductor loop between the locations, anoperating current from the first location over the single conductor loopwhen an electrical communication from the first location to the clientis intact; d) receiving secondarily the operating current through theimpedance when the electrical communication from the first location tothe client is impaired; and e) asserting a break signal when theelectrical communication from the first location to the client isimpaired.

Other features, benefits, and advantages of the present invention willbe apparent upon a review of the present disclosure, including thespecification, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures, in which like reference numerals refer toidentical or functionally-similar elements throughout the separate viewsand which are incorporated in and form a part of the specification,further illustrate the present invention and, together with the detaileddescription of the invention, serve to explain the principles of thepresent invention.

FIG. 1 illustrates a data flow schematic for a battery electronicssystem;

FIG. 2 illustrates a connections schematic for the battery electronicssystem;

FIG. 3 illustrates a general schematic of components of a client;

FIG. 4 illustrates a flowchart of a client response process 400 toreceived serial data;

FIG. 5 illustrates an address byte used in the battery communicationssystem;

FIG. 6 illustrates a packet 6 having 4 bytes used in the batterycommunications system during enumeration;

FIG. 7 illustrates a sequence of address enumeration transmissionsinitiated by the host 105;

FIG. 8 illustrates a detailed general schematic of a signal transmissionportion of a fault signaling subsystem for battery communicationssystem;

FIG. 9 illustrates a detailed general schematic of a redundancy portionof a fault signaling subsystem for battery communications system;

FIG. 10 illustrates a detailed general schematic of an interferencerejection portion of a fault signaling subsystem for a batterycommunications system;

FIG. 11 illustrates an alternate configuration for the host from thatshown in FIG. 10 which adds a filter at each end of the daisy-chainloop;

FIG. 12 illustrates a detailed schematic diagram of an oscillationdamping portion of the power distribution implementation for client;

FIG. 13 illustrates a detail schematic diagram of a wake portion of theclient;

FIG. 14 illustrates a general schematic diagram of a portion of adifferential data signal implementation of battery electronics system;

FIG. 15 illustrates a schematic diagram for a data conductor breakdetection circuit topology that includes a mechanism for data signalbreak detection (i.e., a “break detector”);

FIG. 16 illustrates a schematic diagram for a more generalized conductorbreak detection circuit topology as compared to topology 1500 shown inFIG. 15;

FIG. 17 illustrates a schematic diagram for a power supply conductorbreak detection circuit topology 1700;

FIG. 18 illustrates a detailed general schematic of an interferencerejection portion of a signaling subsystem for a battery communicationssystem similar to FIG. 10 with additional optional details;

FIG. 19 illustrates an alternate configuration for the host from thatshown in FIG. 11 which adds a second host isolated power supply; and

FIG. 20 illustrates an alternate configuration for the host from thatshown in FIG. 19.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention provide a system and method forlow-cost, fault tolerant, EMI robust data communications. The followingdescription is presented to enable one of ordinary skill in the art tomake and use the invention and is provided in the context of a patentapplication and its requirements.

Various modifications to the preferred embodiment and the genericprinciples and features described herein will be readily apparent tothose skilled in the art. Thus, the present invention is not intended tobe limited to the embodiment shown but is to be accorded the widestscope consistent with the principles and features described herein.

There are many different sources and causes of electrical noise in mostevery operating environment. It is not always the case that theelectrical noise interferes significantly with communications withinthat operating environment. Embodiments of the present invention areconfigured and implemented to provide robust communications inelectrically noisy environments. For purposes of this application, anelectrically noisy environment is one in which voltages induced orresulting from the electrical noise in the environment, as measuredbetween nodes or points-under-test, are on the same order of the voltagelevels used for data signaling. In the specific context of anapplication including an electrical motor, such as those used forpropulsion in an electric vehicle (EV), there are significanttime-varying magnetic fields present in regions of the EV that cangenerate significant noise (as voltages and/or currents).

FIG. 1 illustrates a data flow schematic for a battery electronicssystem 100. Battery electronics system 100 includes a host 105 and anumber N clients 110 _(i), i=1 to N. There are many different possibleimplementations and arrangements of host 105 and clients 110 _(x), allwithin the scope of the present invention. To simplify the discussionand as an aid in understanding, the following discussion focuses on aspecific implementation in the context of an electric vehicle (EV)having a battery management system (BMS) and N=8 battery modules, eachbattery module including a battery module board (BMB). The BMS includeshost 105 and each battery module board includes one client 110 _(i), i=1to 8.

Each client 110 _(x) is implemented using commodity processors (e.g.,8-bit microcontrollers) and operates within an architecture designedwith a minimal wire count to achieve the described features. Fullfunctionality of battery electronics system 100 is maintained in theevent of a single wire break or disconnect, with the system operatingsatisfactorily in the presence of EMI having relatively high slew rates.

For data transmissions, host 105 is connected to each client 110 _(x) ina unidirectional daisy-chain loop 115 that begins, and ends, at host105. Clients 110 _(x) are numbered in order that they are connected ondaisy-chain loop 115. Host 105 transmits all commands to a first clienton daisy-chain loop 115 (i.e., client 110 ₁ in FIG. 1). The generalprotocol provides that each client 110 _(i) (e.g., client 110 ₄)retransmits all data it receives on a byte-by-byte basis to a nextclient 110 _(i+1) (i.e., client 110 ₅). The last client in the loop(i.e., client 110 _(N=8)) transmits all data back to host 105. Thus inFIG. 1, host 105 always transmits data to client 110 ₁ and receives fromclient 110 ₈. Battery electronics system 100 does not require anyparticular connection order for battery modules, independent of thepotential (e.g., the modules need not be connected in pack voltageorder). Daisy-chain loops as used in conventional parlance includeswiring schemes in which multiple devices are wired together in asequence or ring. As used herein, daisy-chain includes such wiringschemes, as well as other circular/sequenced wiring schemes in whichdigital data is regenerated or modified and analog signals are processedto counteract attenuation.

FIG. 2 illustrates a connections schematic for battery electronicssystem 100. The connections architecture for battery electronics system100 includes five wires, each wire is terminated at each client 110_(x). These five wires include: a first serial data wire 205, a secondserial data wire 210 (for redundancy), an isolated power wire 215, anisolated ground wire 220, and a fault wire 225. Applications notrequiring fault tolerance and redundant transmission methods use aminimum of three wires: power, ground, and serial data. Thus fourlogical wires connect each client (actually five wires are used becauseof the serial data redundancy). Host 105 and clients 110 _(x) reliablytransmit data over these wires in the presence of substantial EMI witheach client powered by its associated battery module. Each batterymodule is part of a larger potential stack and has a different localground than other battery modules. In the EV there is significantelectrical switching noise, such as from a driver inverter, that createsthe substantial EMI having three forms: switching transients,differential mode noise, and common mode noise.

Host 105 includes a digital signal processor (DSP) that is able to actas a universal asynchronous receiver/transmitter (UART) master. This DSPalso determines the behavior of the battery, calculates a state ofcharge, and other battery metrics and conditions. Clients 110 _(x) andthe communications bus are some of the peripherals that the DSP employsto determine the correct behavior.

In the discussion herein a reference is made to a number of wires orwire count. Reduced wire count is not just desirable because of reducedcomponent cost and decreased manufacturing costs, but also because ofreliability. While FIG. 2 illustrates battery electronics system 100having wire loops, these loops are actually collections of series ofwire segments and connections that extend between host 105 and client110 ₁, between each client 110 _(x), and client 110 _(x+1), and betweenclient 110 _(N) and host 105. These wires have at least two points ofconnection per wire segment, if not more. Connections, whether using aconnector or some joining technique (e.g., crimping), introduces pointsof potential failure having a greater risk of failure as compared to thepossibility that the wire itself may fail. Each wire that is eliminatedtherefore can potentially increase reliability by a significant amount.Any wire that is added must be carefully considered.

FIG. 3 illustrates a general schematic of components included with eachclient 110 _(x). Client 110 _(x) includes a printed circuit board (PCB)305 having a processor 310 (e.g., a commodity 8-bit microcontroller, ora microprocessor, or the like), an ASIC 315, and a set of isolators 320that decouple on-board and off-board signals. PCB 305 includes a numberof wire/connection traces that interconnect the components. Theinterconnections are taken to be reliable in this application so thatthe redundancy of the serial data wires is not replicated on PCB 305.Incoming first serial data wire 205 and second serial data wire 210 arejoined together on PCB 305 for processing. Outgoing first serial datawire 205 and second serial data wire 210 are separated on board PCB 305and then routed out to a downstream device (e.g., host 105 or anotherclient 110 _(x+1)). Each PCB 305 is associated with, and part of, abattery module. Electronics on-board PCB 305 are powered by energyavailable from the associated battery module. Some interface elementsthat are part of PCB 305 are powered from host 105 as further describedherein.

Processor 310 manages communications for client 110 _(x). ASIC 315includes an analog-digital converter (ADC) that measures voltages,temperatures, and other values for each battery module, and it turns ona bleed switch when commanded. It also contains secondary hardwareovervoltage/undervoltage protection. This protection directly triggers alocal fault indication/signal with no interaction with processor 310.

Processor 310 includes a universal asynchronous receiver/transmitter(UART) and is used to implement serial data communications with host 105and clients 110 _(x). UART is broadly adopted in commoditymicrocontrollers and does not require a separate clock signal whichhelps further maintain a reduced wire count and reduced costs.

Each client 110 _(x) includes a set of isolators 320 that decoupleinformation transfer between client-client transfers and client-hosttransfers without a common ground reference. PCB 305 includes fourisolators 320, one for each of inbound serial data (both 205 _((in)) and210 _((in)) are merged and coupled to a data-in signal trace 325 on PCB305), outbound serial data (both 205 _((out)) and 210 _((out)) aremerged and coupled to a data-out signal trace 330 on PCB 305), powerwire 215, and fault wire 225. Some embodiments may reduce this wirecount further, such as by modulating the data signal or the fault signalon top of the power on power wire 215. Some techniques such as, forexample, data whitening, permit toggling of the serial data line at aconstant enough rate to supply power to communications side 335 ofisolators 320.

Isolators 320 as implemented are digital isolators that modulate asignal at a very high frequency (>100 MHz) to produce a high frequencyAC signal. The digital isolator passes this AC signal over a capacitoror an inductor and achieves the desired isolated communication. Opticalisolators are used in some embodiments when the design is not assensitive to cost and power concerns.

Isolators 320 thus isolate a communications side 335 from a local side340. Communications side 335 of every client 110 _(x) are all referencedto the same ground using ground wire 220. Local side 340 is referencedto a ground of the associated battery module supporting PCB 305.Isolators 320 thus transfer information between two different voltagedomains (a communications domain including other devices of batteryelectronics system 100 coupled to communications side 335) and a localdomain including devices of PCB 305 coupled to local side 340).Isolators 320 have a characteristic of being tolerant of these domainsmoving (electrically) relative to each other. An amount of common-modevoltage slew that isolators 320 must withstand varies by application. Inthis case, isolators 320 are able to withstand ˜20 kV/μS of common-modeslew before data transfer between the domains is at risk of corruption.

One way that isolators 320 achieve the desired voltage isolation is thatthey are built using multi-chip-module (MCM) manufacturing techniqueswhich embed multiple semiconductor dies into one substrate and package.Physical differences between the multiple dies of isolator 320 promotethe voltage isolation. ASIC 315 can be built using MCM manufacturingtechniques. In some embodiments of the present invention, thesemiconductor die or dies used for isolator 320 are embedded into thesubstrate and package of ASIC 315 to further reduce use of externalcomponents while achieving desired levels of noise immunity.

As noted above, the general transmission protocol is for host 105 toinitiate all communications by sending commands over the unidirectionaldaisy-chained serial data loops. Further, each client 110 _(x)re-transmits every received command as well as all data responses tothose commands that have been transmitted from downstream clients 110_(y, y<x). Each client may also have a response of its own to transmitas well. Battery electronics system 100 requires a scheme to identifydata packets as the UART does not have a built-in mechanism to frame abeginning and end of data packets.

Each client 110 _(x) implements the UART to receive and transmit thesecommands and responses. The responses, just like the commands, arestreams of response data that will periodically include a series ofbytes that could be interpreted as a command. Battery electronics system100 must implement an easy, low-resource structure and method to detectbeginnings and ends of a packet.

A simple mechanism that may be used in the present context is to use asustained period of complete silence as a mark for the beginning of apacket. Isolators 320 are designed to inhibit spurious bytes from beinginduced on a data wire due to electrical noise. Therefore when host 105is not transmitting and all clients 110 _(x) have re-transmitted allcommands and responses, the data wire is dependably completely silent.The length of time that is required for a command to be circulated fromhost 105 through all clients 110 _(x) is a reference period used forthis period of silence. Host 105 easily frames commands by simplywaiting for a previous command to complete before sending a subsequentcommand.

Clients 110 _(x) also use the period of silence. FIG. 4 illustrates aflowchart of a client response process 400 to received serial data.Process 400 includes steps 405-435. Process 400 begins with a test atstep 405 to determine whether any data is being received. Withoutreceiving data, process 400 loops and repeats the test at step 405 whileassessing a length of time for which no data has been received. However,when the test at step 405 is true (and there is received data), process400 advances to a step 410 to retransmit the received data. After step410, process 400 performs a test at step 415 to determine whether themeasured silence period for data receipt met the predetermined length oftime threshold. When the test at step 415 is negative, process 400returns to step 405 and waits for received data.

However when the test at step 415 is true, process 400 decodes the firstbyte at step 420. A subsequent test at step 425 determines whether thedecoded first byte, which will be an address when the received data is aproperly formed command, matches the stored address associated with theclient. That is, does the first byte suggest that the received data is acommand for this specific client. When the test at step 425 is negative,process 400 returns to step 405 to wait for received data. When the testat step 425 is true, process 400 decodes the next byte or two at step430 to decode the command. Thereafter process 400 performs step 435 toprocess the command, which may require additional bytes of data and mayresult in the client adding a response to the received data. After step435, process 400 returns to step 405 and waits for additional data.

There are other mechanisms that battery electronics system 100 couldimplement for packet framing, including byte stuffing to mark a specificbyte as a start-of-frame delimiter and prevent that particular byte fromappearing in real data. Byte stuffing would be advantageous in allowingcommands to be pipelined on the communications bus and increase busutilization. However doing so requires more processing by the processorsof host 105 and clients 110 _(x).

In communications systems that have a host issuing commands to clientsover a bus, it is common to introduce a signaling system so the host candetermine whether the clients have properly detected and decoded thecommands that have been issued. One mechanism to do this includes use ofacknowledge/not acknowledge (ACK/NAK) responses that the clients provideafter receiving a command. In the present context that includes a hostsending broadcast messages for all clients, it becomes difficult tomanage multiple clients all transmitting ACK/NAK at the same time.

Battery electronics system 100 implements a simple loopback errordetection mechanism. The protocol that is used has each clientre-transmit received commands and responses allowing the host to confirmthat all clients have properly detected and decoded the commands. Inresponse to a command, all the clients sequentially re-transmit thatcommand until the final client re-transmits the command back to thehost. Host 105 compares the received command to the command ittransmitted. When there is a byte-by-byte match, host 105 concludes thatevery client 110 _(x) saw the command as it was sent. No ACK/NAKhandshaking is used.

Battery electronics system 100 requires that each and every client 110_(x) have a unique address so host 105 can unambiguously reference itwith a command. Manufacturing an EV having multiple modules as part ofan energy storage system is simplified when battery modules may bephysically installed with as few requirements and constraints aspossible. Therefore it is preferred that manufacturing not predetermineand set addresses as the modules are installed or that manufacturing notworry about module connection order. Therefore the host and clientsdetermine the addresses at runtime. This can be a challenge as host 105does not have any specific addresses to use when assigning addresses.

Battery electronics system 100 provides a solution that includes havingeach client 110 _(x) start with an address “0” when powered on. Batteryelectronics system 100 considers any client 110 _(x) with an address of“0” as being “unaddressed.” The first byte (of 8 bits) of any packet isan address byte. Two bits of the address byte (e.g., the first andsecond bits) are reserved. One reserved bit is a read/write bit and theother reserved bit is an illegal address bit. The remaining bits providefor a maximum of 62 different useable addresses and thus 62 uniquelyaddressable clients 110 _(x). The following enumeration process(assigning non-illegal addresses to all clients 110 _(x)) uses thegeneral operational transmission rules with one exception. Thatexception not requiring, under a very special set of conditions, thatclient 110 _(x) exactly retransmit received data.

FIG. 5 illustrates an address byte 500 used in battery electronicssystem 100. A first bit 505 is the reserved illegal address bit and asecond bit 510 is the reserved read/write bit. Six low-order bits 515are the address bits of address byte 500. The six bits (000000)-(111111)represent 63 different addresses, with the address (000000) reserved forenumeration leaving 62 operational addresses (000001)-(111111).

FIG. 6 illustrates a packet 600 having 4 bytes used in batteryelectronics system 100 during enumeration. (Packets may have differingarrangements and numbers of bytes in other embodiments.) Packet 600includes a first byte 605 that is an address byte (e.g., address byte500 shown in FIG. 5), a register byte 610, a payload byte 615, and a CRCbyte 620.

FIG. 7 illustrates a sequence 700 of address enumeration transmissionsinitiated by host 105. Host 105 initially sends an enumeration packet705, and it arrives at a client 110 _(x) over first serial data wire205. Enumeration packet 705 includes an address of (000000) with theillegal address bit and read/write bits both set to (0). (This isrepresented in hexadecimal as (0x00).) Also illustrated in FIG. 7 are a“before” address register BAR and an “after address” register AAR. Theseshow the value of an internal memory that each client 110 _(x) uses todetermine its address.

In response to receipt of a packet (e.g., enumeration packet 705) fromhost 105, each client operates using process 400 of FIG. 4. A firstclient 110 _(x) that has an address matching (000000) decodes theremaining bytes which are used to set the desired unique address forclient 110 _(x). In this case, host 105 is changing the address ofclient 110 _(x) from (000000) to (000011) which is also represented as0x03. The BAR for client 110 _(x) is shown as 0x00 and the AAR is 0x03reflecting this change.

Normally client 110 _(x) would retransmit the received packet to client110 _(x+1), but doing so would result in client 110 _(x+1) also havingan address of 0x03. To prevent this, in this special case client 110_(x) retransmits a modified enumeration packet 710. Modified enumerationpacket 710 is exactly like enumeration packet 705 except that theillegal address bit is set high. Thus address byte 500 is changed from(00000000) to (10000000) which is also shown as a change from 0x00 to0x80. Client 110 _(x+1) will decode the address of modified enumerationpacket 710 as (000000) which matches its address, but because theillegal address bit is set, client 110 _(x+1) ignores this packettransmission and does not change its address. Client 110 _(x+1) simplyretransmits modified enumeration packet 710 exactly as it was received.BAR and AAR for client 110 _(x+1) are both shown as 0x00.

This enumeration process is repeated for each client 110 _(x), withaddresses assigned in the order of their connection on the daisy-chainloop. Host 105 eventually receives a loopback in response to thetransmitted enumeration packet 705. As long as host 105 receivesmodified enumeration packet 710 in response, host 105 confirms that aclient 110 _(x) acted upon the enumeration packet 705.

Battery electronics system 100, configured in this way, operates with alatency that is a potential limitation for the number N clients 110_(N). Every client 110 _(x) receives a full byte before transmission,therefore there is a minimum of one byte-time (time to transmit one byteat a chosen baud rate) of latency per client. For a read command that isthree bytes, host 105 must wait N+3 byte-times before receiving a firstbyte of the response. Some applications may be limited by this latencyas N increases.

FIG. 8 illustrates a detailed general schematic of a signal transmissionportion of a fault signaling subsystem for battery electronics system100. As noted above, battery electronics system 100 includes fault wire225 to achieve high safety system reliability. Each battery module isprovided with a mechanism, through its battery module board, to generatea fault signal. This fault signal provides a redundant hardware pathwith respect to data transmission to cause the EV to respondappropriately in the case of a detected fault of the energy storagesystem or one of its components. Fault wire 225 is a shared fault wiredistributing the on-board fault signal to battery electronics system100. Fault wire 225 uses the circular topology of the daisy-chain bus toprovide a dual redundant fault path from each client 110 _(x) to host105.

Each of the N clients 110 must be able to transmit its fault signal tohost 105, and do so reliably. In this example any individual faultsignal generated by any client 110 _(x) is a sufficient condition toalert host 105 of a fault state, therefore the signaling medium mustallow for a “wired OR” summation of all the individual fault signalsfrom all clients 110 _(x). To improve robustness in case of physicaldamage, the signaling medium provides two independent paths to host 105from each client 110 _(x).

In actual implementation, fault wire 225 is installed in a connector andthat connector is used to physically attach to the battery module boardhosting a client 110. Wires are joined to the connector using a crimpterminal. It is sometimes the case that desired levels of reliabilityand costs are not achieved by using a single crimp terminal to join twoor more conductors/wires. To improve reliability and reduce costs, thereis a limitation that no more than a single conductor/wire is associatedwith any crimp terminal which means that each connector circuit cannotbe associated with more than one signal conductor.

To meet all these requirements and connect multiple fault signals to afault wire 225, battery electronics system 100 uses “open collector”signaling for a fault signal transmitter 805 (shown as a transmitterchannel in isolator 320). With open collector signaling, each faultsignal transmitter 805 is capable of sinking current from a signalconductor (e.g., fault wire 225) to ground, but is incapable of sourcingcurrent into the signal conductor. In an IDLE state (no fault signalsare active), fault wire 225 is maintained at a positive power supplypotential, such as by using one or more pull-up resistors 810.

For example, these resistors 810 would be chosen to have a value suchthat the current flowing through them when a potential equal to thedaisy-chain supply voltage is applied to them is close to but less thanthe minimum guaranteed output current of fault signal transmitters 805.This allows fault signal transmitters 805 to reliably drive fault wire225 but provides as much margin for noise current rejection as possible:the larger the current necessary to cause a given voltage drop acrossresistors 810, the smaller the voltage induced by a given noise current.For battery electronics system 100, the parallel combination of thepull-up resistors is 2.375 kOhms, which causes approximately 2 mA ofcurrent to flow when the supply voltage potential of 5V is appliedacross resistor 810. The maximum rated output current of fault signaltransmitters 805 is 4 mA, leaving enough margin to ensure that faultsignal transmitters 805 reach their intended output voltage under allconditions.

Care must be taken in order to guarantee proper digital signalingmargins under all conditions so as to not generate false faultindications while being responsive to any actual fault signal toreliably signal the fault state using fault wire 225. For example, faultsignal transmitter 805 may not be an open collector transmitter. One wayto convert it for open collector operation is to use a diode 815 inseries with an output of fault signal transmitter 805. Having a cathodeof diode 815 coupled to this output and an anode coupled to fault wire225, low voltage on the output of fault signal transmitter 805 tends topull fault wire 225 towards ground, signaling a fault to host 105. A sumof a maximum diode forward voltage at the worst case pull-up resistorcurrent plus the maximum guaranteed output voltage of fault signaltransmitter 805 at the same current is less than a maximum input lowvoltage of receivers at host 105 which are intended to receive the faultsignal.

FIG. 9 illustrates a detailed general schematic of a redundancy portionof a fault signaling subsystem for battery electronics system 100.Conceptually fault wire 225 achieves redundancy using a circulartopology, following the topology of a daisy-chain loop from the host toall the clients and back to the host. The daisy-chain loop begins andends at host 105 with fault wire 225 doing the same. Host 105 includes afirst fault receiver 905 and a second fault receiver 910 for receivingthe fault signal. A break at any one point in fault wire 225 creates twoportions and interrupts only one of the signal paths, a second signalpath to one of the fault receivers of host 105 always exists. Each faultreceiver is provided with pull-up resistor 810 to ensure that eachportion of fault wire 225 assumes the correct IDLE potential when noneof the connected fault signal transmitters 805 are active. When there isno break, the pair of pull-up resistors 810 exist in parallel on faultwire 225 and are accounted for during operation.

The design constraint described herein concerning mechanical joins usingcrimp terminals means that a single wire cannot be literally extended ina complete circuit and make the necessary connections. Thus, fault wire225 is perhaps more properly described as a fault path and is createdusing numerous single wire segments 915. Each PCB 305 supporting client110 _(x) includes a daisy-chain connector 920 and the wire segments 915span that part of the daisy-chain which runs between adjacentdaisy-chain connectors 920. Each daisy-chain connector 920 includes apair of crimp terminals 925, each joins to an end of a wire segment 915.For client 110 _(x), one crimp terminal joins to wire segment 915extending to client 110 _(x−1) and one crimp terminal joins to wiresegment 915 extending to client 110 _(x+1). These segments are eachjoined together using metal traces of PCB 305 coupled to daisy-chainconnector 920. Without this built-in redundancy, the mechanicalconnector design constraints could be problematic as a fault signaloriginating at any client 110 _(x) must enter and exit all intermediateclients 110 _(x) to get to host 105. Given that mechanical connectorsare a common point of failure for electrical systems, the use ofmultiple wire segments 915 could subject the fault signal to multiplemechanical connections in series. The implemented redundancy reduces theattendant risks in this implementation.

The aforementioned redundancy does not protect against progressivedegradation of the mechanical connections in the battery pack which maylead to multipoint failure of the harness, so host 105 must have amechanism for detecting a single point failure of the fault signalingpath and responding appropriately (e.g., preventing continued operationof the vehicle) if the fault signaling redundancy is broken. Since host105 includes two separate fault receivers (receiver 905 and receiver910), each of which should be able to detect a fault signal from any ofthe clients 110 _(x), host 105 may execute a self-test sequence toverify the signaling redundancy. Since the clients 110 _(x) may becommanded to activate the fault signal manually via the daisy-chain datasignals, host 105 can activate each fault signal of each client 110 _(x)in turn and verify that both of the fault receivers detect the faultsignal. Only one client 110 _(x) need be activated to ensure theintegrity of the redundant fault signaling wire all the way around itscircular path, but activating each of the clients 110 _(x) will furthertest each of the fault signal transmitters 805, and guarantee that thefault signaling path is intact from each fault signal transmitter 805 toboth receiver 905 and receiver 910.

All the signal paths (i.e., serial data, power, and fault) are routedthrough an environment having large changes in current in very shortperiods of time as is common for a high voltage battery. Such anenvironment requires care when that route includes a circular signalpath as is implemented in battery electronics system 100. The rapidcurrent changes with respect to time create changing magnetic fieldsthat induce electromotive forces (EMFs) in any conductor that encloses afinite area. The EMF, without proper care, can cause undesired currentto flow in signal conductors or disrupt signals which are encoded asvoltages. A conventional solution for EMF environments provides for useof differential signals for communication as they are unaffected byinduced EMF.

FIG. 10 illustrates a detailed general schematic of an interferencerejection portion of a fault signaling subsystem for battery electronicssystem 100. Signaling in battery electronics system 100 does not usetrue differential signaling as that term is commonly understood. Faultin battery electronics system 100 is transmitted reliably using a singlecircularly routed conductor in spite of induced EMF by making the faultsignal differential with respect to the power and ground conductors.Isolated power wire 215 and isolated ground wire 220 follow the samepath through the battery environment as fault wire 225. This means thatthese signal paths experience the same added EMF as fault wire 225.

Battery electronics system 100 includes a daisy-chain isolator 1005 thatdefines and decouples a first end 1010 of the daisy-chain loop from asecond end 1015 of the daisy-chain loop. Daisy-chain isolator 1005 is ahigh frequency isolator (e.g., a pair of inductors, chokes, or the like)that allows induced EMFs to create a potential difference between firstend 1010 and second end 1015. That potential difference does not causedisruptive current to flow in the daisy-chain loop because of thehigh-frequency isolation.

This potential difference without due consideration could be disruptiveof digital signaling. In battery electronics system 100, digitaltransmitters and digital receivers used at first end 1010 and second end1015 are referenced to only power and ground potentials present at theirrespective ends, both ends powered by an isolated power source (e.g., anisolated DC-DC converter 1020) as further described below. Further, thedigital transmitters and receivers have no connection to the other endof the daisy-chain loop. For example, a digital receiver 1025 ₁ forfirst end 1010 is electrically separated from a digital receiver 1025 ₂for second end 1015. The signaling circuits of battery electronicssystem 100 all include a signal wire (e.g., fault wire 225) and areference potential derived for a reference circuit. In this context, areference circuit means those power and ground circuits supplying therelevant transmitter and receiver. Such signaling circuits of batteryelectronics system 100 do not experience any disruptive potential fromthe EMFs present because the induced EMFs cause any potential to beadded equally to a potential of the signal wire and a potential of thereference circuit.

In battery electronics system 100, each end of the daisy-chain loop isconnected to the remainder of the host 105 circuitry by a separatedigital isolator, whose receivers and transmitters are allowed to assumethe same reference potential as their respective ends of thedaisy-chain, and which serve to translate the received and transmittedsignals of the daisy-chain loop to and from the common referencepotential of the remainder of host 105 circuitry. The daisy-chain endsof these digital isolators are powered by the daisy-chain power andground signals, and the other ends are powered by the common host powerand ground signals used by the remainder of the host circuitry.

FIG. 11 illustrates an alternate configuration for host 105 from thatshown in FIG. 10 which adds a filter 1105 at each end of the daisy-chainloop. In FIG. 10, under some conditions it is possible for spuriouspotentials to appear on fault wire 225 with respect to the referencecircuit. Such spurious potentials can be attributed to many differentcauses but is possibly some type of capacitive coupling. Filter 1105helps to reject such spurious potentials and is preferably implementedas some type of low pass filter. Some implementations may find that asimple RC low pass filter is sufficient, while for otherimplementations, a different filter may be necessary or desirable. Otherfilter types for filter 1105 may include some form of Pi filter to helpaddress any high frequency signals appearing on fault wire 225 viacapacitive coupling.

FIG. 10 also illustrates power distribution for battery electronicssystem 100. The disclosed daisy-chain bus uses active digital circuitryat each client 110 _(x) for voltage isolation. PCB 305 of each client110 _(x) of the disclosed embodiment includes isolators 320 that areimplemented as a packaged digital isolator semiconductor device solution(e.g., “chips” or integrated devices and the like). Battery electronicssystem 100 must distribute power to each client 110 _(x) in order tooperate isolators 320. Battery electronics system 100 implements asimple 5V DC distribution bus.

The daisy-chain bus uses galvanic isolation between the datatransmission medium and nodes originating the data (i.e., host 105 andclients 110 _(x)) therefore a mechanism must be provided to power the“floating” portions of each isolator 320. In FIG. 3, isolator 320includes a communications portion 335 (this is the floating portion) anda local portion 340. The local portion is powered by local power sourcesavailable to each battery module or host. Communications portion 335needs to be powered by a “floating” power source. A convenient form forsuch a power source is isolated DC-DC converter 1020. As shown, oneisolated DC-DC converter 1020 is used to power all nodes which requiresthat conductors be used to distribute the requisite power to all nodes.An alternative would be to install a DC-DC converter at each node andpower each node separately.

Using the single isolated DC-DC converter 1020 requires installation androuting of power wire 215 and ground wire 220 in a daisy-chain loop toeach node. These wires are subject to the same mechanical designconstraints, and potential EMI issues as described herein in the contextof installation and routing of fault wire 225. Similarly to thedistribution of fault wire 225, each wire is actually implemented as asingle path rather than a single conductor. There is a power path and aground path, each path made up of spanning wire segments joined todaisy-chain connectors 920 using crimp terminals 925. Conductive traceson PCB 305 split and route power and ground to each isolator 320.

The daisy-chain topology for the power and ground paths providesredundancy and EMI robustness similarly to the discussion of the faultpath of the daisy-chain loop. A single break does not disable power andground connections for the nodes. Daisy-chain isolator 1005 alleviatesany concerns regarding EMF-induced current flow.

However, in certain circumstances, adding daisy-chain isolator 1005 canresult in unwanted behavior. Specifically, the daisy-chain bus as awhole and the power conductors in particular can act as a single-endedtransmission line with respect to the surrounding metallic elements ofthe battery and battery enclosure. Terminating first end 1010 and secondend 1015 of this transmission line into a high impedance element such asan daisy-chain isolator 1005 changes the modal structure of thetransmission line, and opens up a lowest-order standing wave resonantmode at half of the frequency of that experienced by a transmission linewhose ends are terminated to each other. Specifically, the lowest orderstanding wave mode that can exist on a circular transmission lineconsists of a sine wave of current (or potential) which exhibits onecomplete period of spatial oscillation around the complete circuit ofthe transmission line: this wave will have a temporal frequency equal tothe single ended frequency-dependent propagation velocity of thetransmission line at the frequency of resonance divided by the length ofthe line. A linear unterminated transmission line, on the other hand,can experience a standing wave mode where current (or potential)exhibits a half-period of spatial oscillation over the length of theline. This mode has a temporal frequency equal to the frequencydependent propagation velocity of the single-ended mode of the line atthe resonant frequency divided by twice the length of the line.

If the mutual inductance of the data transmission conductors of thedaisy-chain bus with respect to the power conductors considered as awhole were equal to the self-inductance of the power conductors, thenthe potential gradients experienced by the power conductors duringundriven oscillations of the daisy-chain terminated with high impedancein the above described mode would be matched by identical potentialgradients along the data conductors, and no interfering potentials wouldbe introduced into the data signaling circuit. Unfortunately, since thisis not the case, the data conductors will experience smaller potentialgradients, and those data signaling circuits closest to the currentmaximum of the resonance (the potential gradient maximum, which occursin the middle of the linear transmission line's lowest mode) willexperience induced potentials at the rate of the modal oscillation.These potentials, if large enough, could disrupt digital signaling.Since the lower frequency rate of oscillation of the linear transmissionline's 1st order mode will be closer to the signal frequency and henceharder to reject via filtering than the 1st order mode of the circulartransmission line's resonance, it may be necessary to add damping to theabove described resonant mode of the daisy-chain if inductors are addedto reduce EMF-induced current flow. This can be accomplished byinserting resistors in parallel with the inductors or chokes, connectingone end of the daisy-chain to the other and hence bleeding energy fromthe 1st (and all other odd order) resonant mode(s) when the potentialdifference is at its maximum. This damping effect could also be had byadding distributed or bulk series resistance at other points along thepower conductors of the daisy-chain: but since the object of the powerconductors is to distribute DC power across a distance, added seriesresistance would interfere with their function. In practice, thesignaling rate of battery electronics system 100 is low enough thatadded damping is not necessary, since the lowpass filters that batteryelectronics system 100 insert between each daisy-chain data conductorand its associated data receiver are sufficient to reject theoscillatory potentials associated with the resonance mode describedabove. However, for longer daisy-chains or systems requiring highersignaling rates, such damping may prove advantageous.

FIG. 12 illustrates a detailed schematic diagram of an oscillationdamping portion of the power distribution implementation for client 110_(x). This oscillation damping mechanism addresses a different type ofparasitic oscillation which may arise in a power bus, namelydifferential oscillation of the two power conductors with respect toeach other. In some cases, a distributed reactance in the transmissionlines (e.g., power wire 215 and ground wire 220, here modeled as L_(p))may transmit differential voltage oscillations between power wire 215and ground wire 220. Such oscillations involve current flowing betweenmany decoupling capacitors (represented as C_(DC)) associated withisolators 320. A damping resistance (R_(D)) 1205 is added in seriesbetween each digital isolator 320 and power wire 215. Damping resistance1205 dampens the oscillatory current associated with any parasitictransmission lines. An added benefit of damping resistance 1205 is thatit prevents brief induced transients from reaching isolators 320 whichprotects them from potential sources of damage.

FIG. 13 illustrates a detail schematic diagram of a wake portion ofclient 110 _(x). As discussed herein, isolator 320 addresses electricalnoise and communication between potential deltas in battery electronicssystem 100. Isolator 320 has a drawback in the present application inthat it, when active, consumes power even when no data is actively beingtransmitted. To reduce power consumption, and improve battery standbylife, local side of client 110 _(x) switches “OFF” the power it providesto isolator 320 when no data is being transacted. Consequently host 105must have a mechanism to command client 110 _(x) to restore local powerwhen communications are desired. That mechanism for determining a statusof a host-provided power request signal is referred to herein as “WAKE.”Client 110 _(x) periodically restores power so dedicated logic circuitryon the client can poll the power request signal to determine whetherhost 105 desires to initiate communications. Local power is restored forshort intervals. This ON/OFF cycle for isolator 320 is chosen to reducean average power consumption to as low as possible without sacrificingrequired performance.

Client 110 _(x) includes a pulse generator 1305 that provides a pollingsignal. When communication with host 105 is not active, the pollingsignal determines a status of local power to isolator 320. Periodicallypulse generator 1305 asserts the polling signal (e.g., signal is turned“ON”). When asserted, the polling signal restores power to local side340 of isolator 320, enabling all transmitters and receivers. When notasserted (e.g., signal is turned “OFF”), local power is interruptedwhich disables all transmitters and receivers.

A two-input logic-OR device 1310 (e.g., an “OR” gate) has a first inputcoupled to the polling signal of pulse generator 1305 and an outputcoupled to the power-enabling input of isolator 320. When the output ofdevice 1310 is asserted, isolator 320 is enabled and when the output ofdevice 1310 is not asserted, isolator 320 is disabled. Whenever thepolling signal from pulse generator 1305 is asserted, the output ofdevice 1310 is asserted.

Isolator 320 includes a wake receiver channel 1315 that is coupled to aWAKE signal from host 105. (In the preferred embodiment, power wire 215is coupled to an input of wake receiver channel 1315 with the signallevel of power wire 215 serving as the WAKE signal.) An output of wakereceiver channel 1315 is provided to a second input of device 1310.Whenever the output of wake receiver channel 1315 is asserted, theoutput of device 1310 is asserted. Two conditions must be true for theoutput of wake receiver channel 1315 to be asserted: 1) the WAKE signalmust be asserted by host 105, and 2) wake receiver channel 1315 must beenabled. When wake receiver channel 1315 is disabled, the only way toassert the output of device 1310 is for the polling signal to beasserted. When wake receiver channel 1315 is enabled, assertion ofeither the polling signal or assertion of the WAKE signal from host 105enables wake receiver channel 1315. Enabling wake receiver channel 1315enables all channels of isolator 320, and once enabled, host 105maintains power to isolator 320 for as long as it asserts the WAKEsignal. Deassertion of the WAKE signal returns control of the status ofpower for isolators 320 to individual clients 110 _(x) which maintainisolators 320 active for brief periods to maintain power consumption ata minimum while periodically powering up isolator 320 to check on thestatus of the WAKE signal. By knowing the maximum OFF period of thepolling signal, host 105 need only maintain the WAKE signal active forthis duration to ensure that all isolators 320 in battery electronicssystem 100 are enabled and ready to transmit and receive data.

Fault cannot operate at all if the WAKE signal is not asserted by host105. The reason that this is acceptable it that host 105, in thisapplication, has only one response measure that it can take when thefault signal is asserted: (e.g., it can open the HV switches anddisconnect the HV battery chain from the outside environment). Theprogramming of the hardware and software of host 105 guarantees that itcannot close these HV switches in the first place unless it cancommunicate with the battery modules, and it can't do that unless theWAKE signal has been successfully asserted. So in short, when the WAKEsignal is de-asserted, battery host 105 has no access to the faultsignals of the individual modules: but the host has then already placedthe battery in the safest state that it can attain, so the presence ofthat fault signal would not allow the battery to exhibit any usefulsafety behavior that it does not already exhibit. As an alternateimplementation, the fault signal could be combined with the pollingsignal to turn on the local-side of isolator 320 whenever fault isasserted. This would lower the latency of host 105 receiving the faultsignal when it turns on daisy-chain power. However, it would increasepower consumption of the module in a fault state. Since undervoltage isone potential fault state, this could lead to quicker overdischarge ofbattery modules. Furthermore, the fault state would still not be presentat host 105 until the host turns on daisy-chain power, applying power tothe communication-side of the isolators.

The WAKE signal from host 105 may be more generally used to controlother circuitry of client 110 _(x). For example, a regulator 1320 iscoupled to the output of wake receiver channel 1315. When regulator 1320has a particular state (for instance, when an Enable input contained bythat regulator and connected to wake receiver channel 1315 is driven toa logically true state), processor 310 is powered on, and when regulator1320 does not have the particular state, processor 310 is powered off.In this way, the wake signal has complete control over the power stateof processor 310. Host 105 can immediately power down processor 310 byde-asserting the WAKE signal. Power to processor 310 is restoredwhenever isolator 320 is enabled and the WAKE signal is asserted. Insome embodiments, wake functionality is integrated into othercomponents, such as for example, into isolator 320.

Battery electronics system 100 includes features for increasedreliability in the high energy switching environment of an EV. One ofthose features is strategic and effective redundancy of signal and powerconnections. Detection of failure of a redundant path is desirable.Battery electronics system 100 performs wire break detection on theFAULT signal only by self-testing fault wire 225 at vehicle startup.Some embodiments will implement continuous monitoring of some or allbroken wire failures.

Adding a redundant signal or power conduction path can increase thereliability of a system. In a naïve analysis, replacing a connectionwith a failure rate of η with a parallel combination of two identicalconnections with the same failure rate will result in a total failurerate of η². However, this analysis is based on the assumption of zerocorrelation between failure events, and Poissonian occurrence. Inreality, failure events are not uncorrelated, and often arise fromcommon causes at certain points in time. Such causes might includeincreased humidity, condensation, coolant leaks, sealing failure,periods of excessive vibration, clustered manufacturing processfailures, and the like. Many of these failure causes could lead to bothhalves of a dual redundant system failing within a short time intervalof each other, leading to a combined failure rate much closer to η thanto η². However, it is still likely that the failure events will notoccur at exactly the same time. By detecting failure of the redundancybefore both paths have succumbed to the failure, battery electronicssystem 100 is able to prevent further operation of the vehicle or signalto the driver that a repair is necessary before a dangerous spontaneousloss of function event can occur. Since battery electronics system 100relies on dual conduction paths for a signal or power current in orderto achieve redundancy, implemented methods of wire break detection(which here includes failure of mechanical connector terminals as well)rely on a pre-existent or additional auxiliary test current flowingthrough the circuit to be monitored to detect increases in the circuitresistance, caused by broken or degraded conduction paths. Theseincreases manifest as a voltage change, which can be easily detected.The circuit topologies used by battery electronics system 100 featurelow component count and implementation cost.

There are three types of conductors that battery electronics system 100monitors for redundancy failure: a) data signals (e.g., first serialdata wire 205), b) FAULT signal conductor (i.e., fault wire 225), and c)power conductors (e.g., POWER wire 215).

The basic dual-redundant data signaling path consists of twoelectrically parallel wires running from a transmitter to a receiver.Because these signals contain information over a moderately large rangeof frequencies (data is transmitted at ˜1 Mbps), they need to present arelatively controlled impedance to the transmitter and receiver circuitsfor proper operation. Even though each data signal path itself is asingle wire, battery electronics system 100 forms a differential datasignal path by reference to a parallel power conductor. The differentialdata signal paths formed by each data conductor and its associated powerconductor should be minimally linked by any changing magnetic fieldspresent in the battery, to avoid introduction of spurious potentialsinto the signaling path.

FIG. 14 illustrates a general schematic diagram of a portion of adifferential data signal implementation 1400 of battery electronicssystem 100. Differential data signal implementation 1400 includes a datasignal transmitter 1405 generating a data signal that is divided on PCB305 into a pair of redundant data lines (first serial data wire 205 andsecond serial data wire 210). These signals, with power wire 215 andground wire 220 are configured into differential data signalimplementation 1440 where the data is transmitted to a receiver 1410 ondownstream device.

De-linking the differential data signal paths is accomplished bytwisting one of the signal conductors (e.g., first serial data wire 205)with positive power wire 215, and twisting the other signaling conductor(second serial data wire 210) with negative power wire 220.Additionally, it is desirable to reduce the amount of magnetic fluxlinked with the loop formed by the two data conductors or the two powerconductors, and so it may be desirable to twist the two twisted pairswith respect to each other.

FIG. 14 does not include any break detection circuitry. FIG. 15illustrates a schematic diagram for a data conductor break detectioncircuit topology 1500 that includes a mechanism for data signal breakdetection (i.e., a “break detector”). To achieve break detection,battery electronics system 100 uses the fact that the implemented datatransmission protocol guarantees a certain minimum duty cycle of thetransmitted digital signal. The UART protocol includes a STOP bit foreach transmitted byte, which means that there is at least some positivevoltage present on the data bus every byte interval. This means that thedetection circuit does not need to work with the bus in both states: itcan be designed to work with the bus in the IDLE (STOP bit) state only.Also, because the STOP and IDLE states are the same, the data bus isguaranteed to spend most of its time in this STOP state, increasing thechances that the break detection circuitry will detect any connectionfailure, including transient failures.

The break detector of data conductor break detection circuit topology1500 is based on the base-emitter junction of a single BJT transistor1505, with a PN diode 1510 connected to the base-emitter junction inanti-parallel to allow signal currents of both polarities to passthrough the break detector. Transistor 1505 exhibits predictable V_(BE)values for a given temperature range and test current, and likewisediode 1510 exhibits predictable forward voltage (V_(f)) values for thesame temperature range and current. Battery electronics system 100guarantees that small voltage drops caused by a test current (I_(test))through a good conductor will not cause false failure signals by sizingtest current I_(test) such that the voltage drop incurred by expectedresistances is much less than the minimum expected V_(BE). Moreover,because the maximum V_(BE) and maximum V_(f) are small compared todigital signaling voltages, the voltage lost across the base-emitterjunction should it carry the signaling current is small.

The following discussion relates to transmitter 1405 generating a highvoltage, which is guaranteed to occur at least some of the time asexplained above. Under normal conditions (no breaks in either datasignaling conductor (i.e., first serial data wire 205 or second serialdata wire 210)), a circuit formed by the two signaling conductors keepsthe base-emitter voltage of the transistor 1505 equal to zero. In theevent that the signaling circuit is broken at either a first position1515 in first serial data wire 205 or a second position 1520 in secondserial data wire 210, the current I_(test), which normally flows from anoutput of transmitter 1405 through the signaling circuit to ground, willbe re-routed so that it flows through the base-emitter junction oftransistor 1505. As long as the DC current gain of transistor 1505 issufficiently high, this base-emitter current causes transistor 1505 toconduct. The conduction current produces a voltage across a pull-downresistor R_(pd) that is available at an output node (OUT). Normallyresistor R_(pd) is chosen to have a large enough value that the voltageacross it will rise until transistor 1505 enters saturation, at whichpoint the voltage at the OUT node equals a transmitter output voltageminus a saturation voltage of transistor 1505. The presence of voltageat the OUT node is an indication that the signaling circuit has failed,and that redundancy is lost. OUT may be routed to a digital input of amicrocontroller or other integrated circuit, where it may be monitored.Alternatively OUT may be connected to the fault signaling line in athree-level signaling scheme, discussed herein. Host 105 is able tomonitor all data signaling wire paths at a central location bymonitoring the voltage on FAULT wire 225.

It should be noted that the details of the implementation of FIG. 15 aregeneral in nature with exact implementation details depending on theapplication requirements. For instance, although the DC voltage dropacross the intact signaling conductors in this topology will never beenough to trigger conduction of the B-E junction, transient AC voltagesmay develop across the signaling conductors when transmitter 1405changes its digital output state. Specifically, an inductance in thecircuit formed by the two data conductors on longer cable runs can allowthis voltage to develop. In order to address this issue, a capacitor maybe installed in parallel with the B-E junction. This will provide aconduction path for AC transients, while still allowing the DC componentof I_(test) to activate transistor 1505 in the event a signaling pathinterruption occurs. Care should be taken that any resonant circuitformed by such a capacitor and the inductance of the circuit comprisingthe two data conductors is not under-damped: this could cause activationof transistor 1505. Insertion of a resistance in series with theredundant signaling line could solve the problem.

FIG. 16 illustrates a schematic diagram for a conductor break detectioncircuit topology 1600 as compared to topology 1500 shown in FIG. 15.Topology 1600 includes additional mechanisms for the break detector aswell as three-level fault signaling to host 105. Additionally, FIG. 16includes addition of an AC decoupling capacitor 1605 and a dampingresistor 1610 to the base-emitter junction of transistor 1505. The faultsignaling polarity of FIG. 16 is opposite of the fault signalingpolarity shown in FIG. 8. Use of a simple inverter (e.g., anothertransistor or digital IC or the like) makes either scheme compatiblewith other.

Topology 1600 includes the redundancy data and redundancy failure signalimplementations described herein with a continuous fault break detectionsignal that allows host 105 to centrally detect any failure of a data orsignaling wire anywhere in battery electronics system 100.

Topology 1600 includes an emitter-follower transistor 1615 in client 110_(x), transistor 1615 having an emitter coupled to power wire 215, abase coupled to the collector of transistor 1505, and a collectorcoupled to fault signal transmitter 805. Host 105 includes a resistivedivider 1620 (e.g., three series resistors R_(SA)˜49 kΩ, R_(SB)˜5 kΩ,and R_(SC)˜1 kΩ), a window comparator 1625, and a fault detector 1630all coupled to both ends of fault wire 225.

Transistor 1615 applies a voltage to fault wire 225 whenever any datawire fails. This voltage is approximately one diode drop (e.g., ˜0.6V).When a fault wire 225 fails, resistive divider 1620 (which also acts aspull-down resistor R_(pd)) generates a similar voltage level at a testnode 1635. Window comparator 1625 monitors test node 1635 and when thevoltage is at level that indicates a break, window comparator 1625asserts a broken wire signal. (In this case, window comparator 1625asserts the broken wire signal when the voltage at test node 1635 is notbetween 0.1V and 0.25V.) Assertion of the broken wire signal is awarning signal that data or fault wire redundancy has been lostsomewhere in battery electronics system 100 and is available at host105.

Window comparator 1625 has the additional function of monitoring thefault wire for short circuits to one of the two power conductors. Anyaccidental connection, or “short” of the fault wire, can impede itsnormal function. Since the fault wire signals potentially dangerousconditions by changing its potential (from a low potential to a highpotential, in the case of topology 1600), any short that connects thefault wire electrically to a potential that is the same as thatpotential which an operable fault wire normally uses to signal theabsence of dangerous conditions can mask the true presence of dangerousconditions by preventing the fault wire from attaining that potentialwhich is normally used to signal them. In the embodiment described intopology 1600, connection of the fault wire to the ground conductor ofthe daisy-chain, or to any metallic object which is at or below thepotential of the ground conductor, can cause the potentially harmfulcondition described above. It can be seen that the resistive divider1620 will cause the fault signal to normally attain a potential that isequal to neither the power conductor nor the ground conductor, but issomewhere in between. In the described topology, the resistive divider1620 is designed so that the fault wire will normally attain a potentialwhich is between the two thresholds of the window comparator, andpreferably equidistant from them. In topology 1600, this potential thatthe fault wire normally attains when no faults or broken wires aresignaled is 0.175V. By implementing a window comparator 1625 that candetect when the potential on the fault wire falls below a lowerthreshold, here depicted as 0.1V, the window comparator may signal notonly when the fault wire has been broken as described above, but alsowhen the fault wire has short-circuited to ground, and is incapable ofsignaling a fault. This condition of “shorted to ground” may beconsidered potentially more dangerous than a broken fault wire, since inthe first case no fault at all may be signaled while in the latter caseit's probable that a fault signal would still reach one of the twointended redundant receivers. Therefore, an implementation may desire toreplace the window comparator 1625 depicted herein with two separatelevel comparators, one of which signals passage of the fault signalthrough an upper threshold, and the other through a lower threshold.These two thresholds described correspond to the thresholds of 0.1V and0.25V depicted in topology 1600 and associated with window comparator1625. The upper threshold comparator would continue to generate a“BROKEN WIRE” signal as is generated by the window comparator intopology 1600, while the lower comparator would now generate a “SHORTEDFAULT WIRE” signal: battery host 105 would then be able to reactappropriately to these two different conditions.

Should any client 110 _(x) generate a true FAULT signal from faultsignal transmitter 805, voltage on fault wire 225 rises to a greaterlevel and the voltage at test node 1635 also rises. The voltage at testnode 1635 is monitored by fault detector 1630 and when it rises above asecond threshold (e.g., 0.25V), fault detector 1630 asserts a FAULTsignal. The FAULT signal at host 105 is an alert that one of the Nclients 110 _(x) has asserted a true FAULT signal.

If necessary or desirable, it is possible to incorporate wire breakdetection on the power supply conductors. FIG. 17 illustrates aschematic diagram for a power supply conductor break detection circuittopology 1700. One way to achieve such wire break detection is bycompleting the redundant power supply path with a pair of diodes (afirst diode 1705 connecting the two ends of the power connections, and asecond diode 1710 connecting the two ends of the ground connections).These diodes will normally have no voltage across them, because the mainconduction path (the path from DC-DC converter through daisy-chainisolator 1005 and around the loop) will supply current to the entiredaisy-chain with little voltage drop. If either power conductor isbroken, its associated diode will conduct current, and the forwardvoltage across this diode may be measured by a comparison circuit 1715.A single differential comparator 1720 would be sufficient to make themeasurements of both diode voltages. A few resistors (e.g., R_(A) andR_(B), R_(A) slightly greater than R_(B) for example R_(A)=50 kΩ andR_(B)=49 kΩ) and capacitors (e.g., a pair of diode bypass transistorsC_(BP) and a pair of filter capacitors C_(f)) would be necessary tosuppress momentary AC voltages which could be caused by reactiveimpedance of the power supply conductor loop or induced voltage fromEMFs. Generally, a resonant circuit formed between the two diode-bypasscapacitors and the power conductor loop will be found to be stronglyunder-damped. A series C or RC circuit may need to be added between thecathode of the diode on the power-loop and the anode of the ground-loopdiode. This pair of diodes could be replaced by base-emitter junctionsof bipolar junction transistors, as was done for the data breakdetection discussed herein. It will likely be found that BJTs whose BEjunctions are rated for the necessary current to supply the multipledigital isolators required by the daisy-chain loop are hard to come by,and therefor unlikely to be commodity items, and hence a more expensivesolution that typically renders it unsuitable for battery electronicssystem 100 of an EV.

FIG. 18 illustrates a detailed general schematic of an interferencerejection portion of a signaling subsystem for a battery communicationssystem similar to FIG. 10 with additional optional details. Explicitlyincluded in FIG. 18 is use of a first digital isolator 1805 ₁ at firstlocation 1010 and a second digital isolator 1805 ₂ at second location1015 for redundant multistate signaling (e.g., FAULT) and datacommunications with respect to the communications master of host 105.First digital isolator 1805 ₁ supports FAULT₁ signaling and transmissionof data (DATA(OUT)) to clients 110 and second digital isolator 1805 ₂supports FAULT₂ signaling and receipt of data (DATA(IN)) from clients110. As noted, in some implementations it is desired to have two or moredaisy-chain loops for data communications but to simplify FIG. 18, onedata daisy-chain loop is illustrated. Also illustrated is a processor1810 for each client (similar to processor 310) receiving host-initiatedcommunications from an upstream communications device and transmittingto a downstream communications device over the daisy-chain loop andending back at host 105.

FIG. 19 illustrates an alternate configuration for host 105 from thatshown in FIG. 11 which includes a first host isolated power supply 1905at first location 1010 and adds a second host isolated power supply 1910at second location 1015. Each client 110 is able to receive power fromboth power supplies, and a single break in one of the conductors doesnot remove operating power as one of the power supplies will alwaysremain coupled. This powers redundant multistate signaling (e.g., FAULT)at both locations as well.

FIG. 20 illustrates an alternate configuration for host 105 from thatshown in FIG. 19. Included in this implementation is use of thesimplified fault receiver mechanism of FIG. 9 for the redundant secondfault receiver function. This simplified fault receiver arrangement usesa single power supply 1020 and one ground-referenced fault receiver(e.g., receiver 910) and eliminates daisy-chain isolator 1005.

The system and methods above has been described in general terms as anaid to understanding details of preferred embodiments of the presentinvention. In the description herein, numerous specific details areprovided, such as examples of components and/or methods, to provide athorough understanding of embodiments of the present invention. Forexample, in the application the term “processor” is used to not onlyrefer to microprocessors, microcontrollers, and other similarorganizations of electronic circuitry, but includes for purposes of thisapplication an electronic circuit capable of executing instructionsaccessed from a memory. Data processing system is sometimes used hereinto explicitly connote this broader context, but absent specific contextto the contrary, uses of “processor” and similar are not limited tothese particular arrangements of electronic circuitry. Some features andbenefits of the present invention are realized in such modes and are notrequired in every case. One skilled in the relevant art will recognize,however, that an embodiment of the invention can be practiced withoutone or more of the specific details, or with other apparatus, systems,assemblies, methods, components, materials, parts, and/or the like. Inother instances, well-known structures, materials, or operations are notspecifically shown or described in detail to avoid obscuring aspects ofembodiments of the present invention.

Reference throughout this specification to “one embodiment”, “anembodiment”, or “a specific embodiment” means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the present invention and notnecessarily in all embodiments. Thus, respective appearances of thephrases “in one embodiment”, “in an embodiment”, or “in a specificembodiment” in various places throughout this specification are notnecessarily referring to the same embodiment. Furthermore, theparticular features, structures, or characteristics of any specificembodiment of the present invention may be combined in any suitablemanner with one or more other embodiments. It is to be understood thatother variations and modifications of the embodiments of the presentinvention described and illustrated herein are possible in light of theteachings herein and are to be considered as part of the spirit andscope of the present invention.

It will also be appreciated that one or more of the elements depicted inthe drawings/figures can also be implemented in a more separated orintegrated manner, or even removed or rendered as inoperable in certaincases, as is useful in accordance with a particular application.

Additionally, any signal arrows in the drawings/Figures should beconsidered only as exemplary, and not limiting, unless otherwisespecifically noted. Furthermore, the term “or” as used herein isgenerally intended to mean “and/or” unless otherwise indicated.Combinations of components or steps will also be considered as beingnoted, where terminology is foreseen as rendering the ability toseparate or combine is unclear.

As used in the description herein and throughout the claims that follow,“a”, “an”, and “the” includes plural references unless the contextclearly dictates otherwise. Also, as used in the description herein andthroughout the claims that follow, the meaning of “in” includes “in” and“on” unless the context clearly dictates otherwise.

The foregoing description of illustrated embodiments of the presentinvention, including what is described in the Abstract, is not intendedto be exhaustive or to limit the invention to the precise formsdisclosed herein. While specific embodiments of, and examples for, theinvention are described herein for illustrative purposes only, variousequivalent modifications are possible within the spirit and scope of thepresent invention, as those skilled in the relevant art will recognizeand appreciate. As indicated, these modifications may be made to thepresent invention in light of the foregoing description of illustratedembodiments of the present invention and are to be included within thespirit and scope of the present invention.

Thus, while the present invention has been described herein withreference to particular embodiments thereof, a latitude of modification,various changes and substitutions are intended in the foregoingdisclosures, and it will be appreciated that in some instances somefeatures of embodiments of the invention will be employed without acorresponding use of other features without departing from the scope andspirit of the invention as set forth. Therefore, many modifications maybe made to adapt a particular situation or material to the essentialscope and spirit of the present invention. It is intended that theinvention not be limited to the particular terms used in followingclaims and/or to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include any and all embodiments and equivalents falling within thescope of the appended claims. Thus, the scope of the invention is to bedetermined solely by the appended claims.

1-14. (canceled)
 15. A battery electronics system comprising: a hostcircuitry serving as a host in the battery electronics system; multipleclient circuitries, each serving as a client in the battery electronicssystem and assigned to a respective one of multiple battery modules; oneor more conductors forming a daisy-chain loop that begins at the hostcircuitry, extends to each of the client circuitries in sequence, andends at the host circuitry, wherein the host is configured to send,through the daisy-chain loop, a packet having a start-of-packetidentifier defined by a period of signal inactivity; and in each of themultiple client circuitries: a receiver configured to receive, throughthe daisy-chain loop, a transmission having an initial period of signalinactivity and a subsequent period of signal activity; and a comparatorconfigured to compare the initial period of signal inactivity to thesubsequent period of signal activity.
 16. The battery electronics systemof claim 15, further comprising an address register in each of theclient circuitries, wherein a common value is initially stored in eachof the address registries, the common value indicating that thecorresponding client is unaddressed in the battery electronics system,wherein the host is configured to send an enumeration message to causeassignment of a non-illegal address to one of the clients.
 17. Thebattery electronics system of claim 16, wherein the one of the clientsstores a new address from the enumeration message in its addressregister and sends a modified enumeration message to a next one of theclients in the daisy-chain loop, the modified enumeration messageinstructing the next one of the clients not to update its addressregister based on the modified enumeration message.
 18. The batteryelectronics system of claim 17, wherein each of the client circuitriesimplements a data transmission protocol in which any of the clients thatreceives the packet directly from the host, or from a next clientupstream in the daisy-chain loop, shall retransmit the received packetwithout modification to a next client downstream in the daisy-chainloop, or directly to the host, and wherein the data transmissionprotocol makes an exception for sending the modified enumeration messagein response to receiving the enumeration message.
 19. The batteryelectronics system of claim 15, wherein the conductors include at least:a serial data wire, a redundancy data wire, a power wire, a ground wireand a fault wire.
 20. The battery electronics system of claim 15,further comprising, in each of the client circuitries, a break detectioncircuit for the one or more conductors.
 21. The battery electronicssystem of claim 15, further comprising an isolator circuit in each ofthe client circuitries, each of the isolator circuits having acommunications side toward the one or more conductors, and a local sidetoward the respective client circuitry.
 22. The battery electronicssystem of claim 21, wherein the client circuitry is configured to turnoff power to the local side unless: (i) communication with anotherclient or the host is active, or (ii) the client circuitry is pollingthe one or more conductors, or (iii) a wake receiver channel of theisolator circuit asserts a wake signal from the host.
 23. The batteryelectronics system of claim 15, further comprising two receivers in thehost circuitry such that upon an interruption of the one or moreconductors, a signal path exists to the host circuitry from each of theclient circuitries.
 24. The battery electronics system of claim 15,wherein at least a portion of the one or more conductors is routedthrough a region of an electrically noisy environment having atime-varying magnetic field capable of generating a noise induced signalhaving a peak magnitude on an order of a threshold magnitude of datasignals transmitted over the one or more conductors.
 25. A methodcomprising: sending, from a host in a battery electronics system, apacket having a start-of-packet identifier defined by a period of signalinactivity, the battery electronics system including one or moreconductors forming a daisy-chain loop that begins at the host, extendsto each of multiple clients in sequence, and ends at the host; receivingthe packet in each of the multiple clients, each client receiving thepacket either directly from the host or from a next client upstream inthe daisy-chain loop, the packet having an initial period of signalinactivity and a subsequent period of signal activity; and comparing, ineach of the multiple clients, the initial period of signal inactivity ofthe start-of-packet identifier to the subsequent period of signalactivity.
 26. The method of claim 25, wherein each of the clients has anaddress register and wherein a common value is initially stored in eachof the address registries, the common value indicating that thecorresponding client is unaddressed in the battery electronics system,the method further comprising sending, from the host, an enumerationmessage to cause assignment of a non-illegal address to one of theclients.
 27. The method of claim 26, further comprising storing a newaddress from the enumeration message in the address register of the oneof the clients, and sending a modified enumeration message to a next oneof the clients in the daisy-chain loop, the modified enumeration messageinstructing the next one of the clients not to update its addressregister based on the modified enumeration message.
 28. The method ofclaim 27, wherein the method comprises retransmitting the packet withoutmodification from any of the clients to a next client downstream in thedaisy-chain loop, or directly to the host, except when sending themodified enumeration message in response to receiving the enumerationmessage.
 29. The method of claim 25, further comprising performing breakdetection for the one or more conductors in each of the clients.
 30. Themethod of claim 25, further comprising isolating, in each of theclients, a communications side toward the one or more conductors from alocal side toward the respective client.
 31. The method of claim 30,further comprising turning off, in each of the clients, power to thelocal side unless: (i) communication with another client or the host isactive, or (ii) the client is polling the one or more conductors, or(iii) the host sends a wake signal.